It is known that in the preparation of dye solutions intended for use in the textile industry, a predetermined amount of dyes in powder, granules or micropearl form is mixed with water or other suitable solvent. The said solution is prepared within a vessel into which the dyeing materials are introduced by controlling their weight by means of a precision scale, the vessel being transferred afterwards in correspondence of a dissolution station which includes a solvent-delivering conduit and mixture-stirring means. The thus obtained solution is then either sucted and conveyed to the selected user or stored within a storage container. Documents IT TO92A960 EP93118274 and U.S. 583726, all of the same owner, disclose a device for the preparation of dye solutions which comprises, in combination, a vessel into which a batch of the product to be dissolved and a predetermined amount of solvent are made to flow, and a structure vertically movable to and away from the said vessel, said structure supporting a conduit for delivering said solvent and means for stirring the product-solvent mixture, said means resulting, during the preparation of the solution, in lowered position and dipped into the said vessel. The said conduit and said stirring means are housed within the cavity of a bell-shaped body which, during the preparation of the solution, has its respective lower base portion dipped into a substantially annular tank which encircles the base of said vessel so as to prevent any leak of liquid from coming in contact with the environment when the stirring means are in operation. Moreover, said vessel is rotatively mounted about the respective central vertical axis to cooperate with the stirring means for the preparation of the solution, particularly upon a stage of treating the paste obtained with the initial admission of the solvent into the vessel.
However, said known device exhibits some technical drawbacks, among which the fact of needing a complex mechanical structure for the vertical displacement of said stirring means and a structure overweight due to the presence of the protection bell and of the tank which surrounds the vessel ensuring the necessary isolation of the latter from the external environment. Moreover, it is necessary to operate in a controlled way also the rotation of the same vessel during the preparation of the solution. All this inevitably implies increasing the cost for the fabrication and the overall maintenance of the plant for the production of the liquid dyes.
Patent FR 1507155 discloses a mixer of the same type, with a vessel intended to hold the mixture and provided with stirring means associated to a support vertically guided towards and away from the vessel.
Also the patent EP 13882 describes a device based upon the same operating principle set forth above.
Moreover, patent U.S. Pat. No. 4,095,287 discloses a device for preparing materials in paste form and which comprises a vessel intended to hold the material to be mixed, and means for mixing said material which are supported by an element associated to corresponding means for vertical movement towards and away from the vessel itself, the latter rotating about its own central vertical axis to assist the mixing means for the preparation of the paste.
But also these known devices technical exhibit drawbacks due to the necessity of lifting and lowering every time the assembly of stirring or mixing means.